stevebez

Has anyone done 5th gear dyno pulls to simulate larger loads? This would give us much better insight as to whats going on at higher rpm for longer duration WOT run and AFR's ... and fuel starvation issues?

jmb614

IIRC AFR's should be the same no matter which gear you pull from. Someone please correct me if I'm wrong.

mikeevo

You want to use which ever gear gives you a 1:1 ratio to be most accurate, but as long as you pull in the same gear when you make changes it doesnt matter. I have seen it make almost no difference less than 5HP difference between gears 2,3,4,5 . I have seen it make 20-30hp difference between gears. Just be consistent if your after true changes. pick any gear you want if your looking for a big number on a piece of paper.

GT-ER

I'd do 4th gear max. 5th gear would just take way too long and dyno's tend to have poor ventilation. The car could overheat.

TTMotorsports

Excellent thought Steve but in order to see the fuel starvation issue you would have to have EGT probes in each cylinder to see the temps in each. Another point of data to use would be IDC's since the fuel starvation issue is apparent in high load gears(top of 3rd, all of 4th and 5th) when the IDC's are well past the threshold to be labeled static.

Larger injectors will lower your IDC's but will do nothing for the volume that is needed on modified M113k's. 12" of more volume and consistent fuel pressure to all injectors is what the TTM fuel rail accomplishes.

The a/f's are an average of 4 cylinders if you use a wideband in each side of the exhaust. Even if #5 is rich, 6&7 closer to optimum a/f's that you are targeting and 8 is lean(fuel starvation), the average a/f will look good according to a wideband.

GT-ER

Has anyone even monitored fuel pressure to see if it goes down considerably?

GT-ER

True, and for the price of getting that EGT setup you may as well just buy the injectors and fuel rail and be happy.

jmb614

I haven't logged it personally, but I believe there may be a pressure drop from 80 to 65psi when the engine hits 5K rpm.

TTMotorsports

You are learning way too much for your own good Jason! I guess when you street tune with Jerry for a whole day you pick up some info!

skratch77

I think you guys are tuning way to lean still.here is my dyno.

TTMotorsports

Do you have a wide band O2?

10.88 is very rich and safe. That is not even close to optimum Angelo. That is a very conservative tune.

skratch77

Im happy with it and the car is consistant at the track.

I wanted it safe because of all the people blowing up there engines.Honeslty I lost maybe 8-10whp going a full point richer and that is worth it for piece of mind over braging numbers.

This dyno also reads very low so add about 30-40 whp for dynojet numbers.I think it made 467whp with 11.8 a/f up top.

Iv dynod the car over 10 times and going to almost 2 points leaner was not more than a 15whp difference.

Timing and keeping the intake cold is what makes power.

tbal

Are afr's suppose to be same from every gear pull? What would be safe numbers?

Jakpro1

Doesn't 4th take you upwards of 190+ at redline? 5th gotta be well over 200mph. Can the rollers take that?

jmb614

My tune is currently on the lean side, you are correct Scratch. However, Jerry isn't done with it. I would like to see 11.2-11.5 personally.

And Bruce, I have learned quite a bit tuning with Jerry, but it was you who gave in depth fueling info

skratch77

Just tell him to tune it on the safe side,like what if you s/c pump fails and your engine sees 190+ iat's with that 185 pulley,You dont have much room in there before something lets go.

I would ask how much timing you are running from 4800 to redline at full load and make sure its not to agressive with that 185 beast you got on there.

Ohh and you are nuts running a 185 with stock headers lol get some headers on there asap!!!

jmb614

I have timing logs from the dyno, timing is good. Yeah I definitely need headers...

jmb614

I datalog IAT's among other things constantly.

skratch77

Here is my car with a/f in the 12s up top and it still made 46x whp

jmb614

Yeah, I'll gladly sacrifice a nominal amount of horsepower for safety.

Jakpro1

WOW! Leaving 40whp just sitting there bro. Get some headers on that puppy.

skratch77

I have kleemann headers renntech airbox,python tubes,ttm scoops,Big heatexchanger blah blah etc..

My dyno reads low,am at an easy 500+whp on a dynojet

I kinda like saying a ran 11.3 with 457whp tho

jmb614

Lol, so true.

jmb614

Honestly though, I would feel comfortable running 11.5-11.8 up top with the fuel rail/injectors setup. Knowing that all 8 are getting the same amount of pressurized fuel greatly reduces the risk.

stevebez

The thing is just because the injectors hit max duty cycle does not imply you are running lean it may be the map throwing fuel to cool things down typical of a long duration dyno run and a long duration wot run.

To get the right power readings sure you need something that gives a good 1:1 ratio which is typically 4th for 2.65 diff guys. But this is not what I am trying to simulate here ... not a power reading but more to watch IDC and AFR's.... reading each cylinder would be ideal but not exactly practical! But I guess we need to start somewhere....

Strapping a fuel pressure guage to the test point over a dyno run could also provide invaluable info for us ... any one done this and overlay the data with AFR /IDC's?

Suppose all we need to do is manually activate the fuel delivery system and injectors to max duty cycle and test the pressure at this point...? May not need a dyno run to do this... if our pressure drops off hard - we then need to test with 2 pumps... and see how that goes but we need adequate FPR's in place.

The heat build up is kind of exactly what I want to simulate as we can then see how the map is behaving, IDC, and how the fuel pressure scenario behaves... seeing fuel pressure drop from 80psi to 65psi at 5000 rpm is a major concern and may mean its our pump which cannot keep up rather than the injector and fuel rail setup... remember the SLR has dual pumps, and marginally larger injectors than our cars (is this right?), but does have a looped fuel rail, but also a fully regulated fuel pressure setup.... which we seem to be woefully missing ..... (or am I wrong here too?)

This really is the solution for us....

A fully regulated fuel delivery system similar to the SLR

So....
1). Closed loop rail
2). two Regulators, with return lines
3). Dual Pumps
4). On the injectors I'm not so sure but could be anything up to SLR delivery capacity as these can be scaled to the map thats being used, but I guess I would start with stock and test with the above mods in place.

6175rpm on 2.82 diff with 275/30/19 wheels is good for around 200mph.... dyno how dynos deal with that...